The present invention relates to a press for the production of plastic blanks, particularly unfinished ceramic shapes for insulators, and more especially, a press having a feed installation.
Presses of the aforementioned type are known. Even though much effort has been expended, even to this day screw presses are the most frequently employed tools for the shaping of plastic materials, such as those used, for example, in the ceramic industry or in the building material industry in brick plants. See, Sprechsaal, Vol. 116, No. 1, 1983, Fachberichte, page 25 et seq. These presses, also known as extrusion presses, have always been criticized, since all types of screw presses are burdened by a number of disadvantages, which are unacceptable depending upon the particular application range of a given press. This state of the art has already been described in Swiss Patent No. 33 45 52 and the principal disadvantages, which still exist, are listed therein.
A possibility of obtaining satisfactory pressing results, while simultaneously avoiding the negative accompanying phenomena of screw presses, is offered by a press which has become known in about 1972 as the screw-less extrusion press. This press employs a roll-shaped conveying member, the so-called rotor. This roll shaped conveying member is equipped over its entire length with annular grooves normal to the axis, wherein the plastic material is moved in the circumferential direction of the conveying member. The roll shaped member rotates with a slight play in a horizontal cylindrical housing, while a feed roll fills the annular grooves. In the individual grooves tangentially located strippers are arranged, which remove the plastic material at the outlet from the roll and the grooves. Even though this rotary press teaches a configuration in which a screw is no longer used as the pressure generating and material transport element, this principle of construction has been unable to displace the screw press.